Method And System For Using Public Land Mobile Network Identifier To Maintain Device Service In A Network

1. A method for controlling operation of a user equipment device (UE) in a wireless communication system comprising a first radio access network (RAN) and a second RAN, wherein the first RAN has a plurality of base stations configured to provide service according to a first air interface protocol, wherein the second RAN is configured to provide service according to a second air interface protocol, and wherein the first RAN has an interconnection with the second RAN, the method comprising: detecting, by a UE, broadcast of a public land mobile network identifier (PLMN ID) by a base station of the plurality, wherein the base station does not support circuit switched fallback (CSFB) between the first RAN and the second RAN, and wherein the detected PLMN ID is of a home service provider of the UE; determining by the UE whether the detected PLMN ID of the home service provider has a predefined value that is associated with operating in a Single Radio Long Term Evolution (SRLTE) mode in which (a) the UE is served by the base station for data service even though the base station does not support CSFB and (b) the UE is set to engage in voice calls served directly by the second RAN; and controlling by the UE, based on the determination of whether the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode, whether the UE operates in the SRLTE mode or rather operates in a CSFB mode in which, because the base station does not support CSFB, the UE declines to be served by the base station and is served directly by the second RAN, wherein if the determination is that the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode, then the UE operates in the SRLTE mode, and if the determination is that the detected PLMN ID of the home service provider does not have the predefined value associated with operating in the SRLTE mode, then the UE operates in the CSFB mode.

2. The method of claim 1 , wherein the home service provider has a first PLMN ID having the predefined value and a second PLMN ID having a second, different predefined value, wherein determining whether the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode comprises determining whether the detected PLMN ID of the home service provider has the predefined value rather than the second predefined value.

3. The method of claim 1 , wherein controlling, based on the determination of whether the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode, whether the UE operates in the SRLTE mode or rather operates in the CSFB mode comprises causing the UE to operate in the SRLTE mode only if the determination is that the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode.

4. The method of claim 1 , wherein controlling, based on the determination of whether the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode, whether the UE operates in the SRLTE mode or rather operates in the CSFB mode comprises: first determining by the UE that the base station does not support CSFB, responsive to determining that the base station does not support CSFB, then determining whether the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode, and controlling by the UE, based on the determination of whether the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode, whether the UE operates in the SRLTE mode or rather operates in the CSFB mode.

5. The method of claim 1 , wherein the UE operates in the SRLTE mode if both (i) the determination is that the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode and (ii) the predefined value indicates that the base station does not support CSFB.

6. The method of claim 1 , wherein operating in the SRLTE mode further comprises the UE registering to be served by the second RAN without the UE engaging in registration signaling with the second RAN over the interconnection between the first RAN and the second RAN.

7. A method for controlling operation of a user equipment device (UE) in a wireless communication system comprising a first radio access network (RAN) and a second RAN, wherein the first RAN has a plurality of base stations configured to provide service according to a first air interface protocol, wherein the second RAN is configured to provide service according to a second air interface protocol, wherein the first RAN has an interconnection with the second RAN, wherein the UE has two mutually exclusive modes of operation including a circuit switched fallback (CSFB) mode of operation and a Single Radio Long Term Evolution (SRLTE) mode of operation, wherein operating in the CSFB mode comprises, when the UE detects coverage of a given base station of the plurality and when the given base station does not support CSFB between the first RAN and the second RAN, the UE responsively declines to be served by the given base station and the UE instead becomes served directly by the second RAN, and wherein operating in the SRLTE mode comprises (i) the UE being served by a given base station of the plurality for data service even though the given base station does not support CSFB and (ii) the UE being set to engage in voice calls served directly by the second RAN, the method comprising: operating by the UE in the CSFB mode; detecting by the UE broadcast of a public land mobile network identifier (PLMN ID) by a base station of the plurality, wherein the base station does not support CSFB, and wherein the detected PLMN ID is of a home service provider of the UE; determining by the UE that the detected PLMN ID of the home service provider has a predefined value associated with operating in the SRLTE mode; and in response to the determination that the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode, the UE switching from operating in the CSFB mode to instead operating in the SRLTE mode.

8. The method of claim 7 , further comprising: before determining that the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode, determining by the UE that the base station does not support CSFB, wherein determining that the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode is performed in response to the determination that the base station does not support CSFB.

9. The method of claim 7 , further comprising: determining that the detected PLMN ID of the home service provider indicates that the base station does not support CSFB, wherein switching from operating in the CSFB mode to instead operating in the SRLTE mode is performed further in response to the determination that the detected PLMN ID of the home service provider indicates that the base station does not support CSFB.

10. The method of claim 7 , wherein the operating, the detecting, and the determining are performed while the UE is not being served by the base station, and wherein operating in the SRLTE mode further comprises the UE engaging in signaling with the base station to register the UE with the base station.

11. A user equipment device (UE) comprising: a first radio configured for the UE to be served by a first radio access network (RAN) according to a first air interface protocol, wherein the first RAN has a plurality of base stations configured to provide service, and wherein the first RAN has an interconnection with a second RAN; a second radio configured for the UE to be served by the second RAN according to a second air interface protocol; and a control unit configured to (i) detect broadcast of a public land mobile network identifier (PLMN ID) by a base station of the plurality, wherein the base station does not support circuit switched fallback (CSFB) between the first RAN and the second RAN, and wherein the detected PLMN ID is of a home service provider of the UE, (ii) determine whether the detected PLMN ID of the home service provider has a predefined value that is associated with operating in a first mode, and (iii) control, based on the determination of whether the detected PLMN ID of the home service provider has the predefined value associated with operating in the first mode, whether the UE operates in the first mode or rather operates in a second mode, wherein if the determination is that the detected PLMN ID of the home service provider has the predefined value associated with operating in the first mode, then the UE operates in the first mode, and if the determination is that the detected PLMN ID of the home service provider does not have the predefined value associated with operating in the first mode, then the UE operates in the second mode, wherein the first mode is a Single Radio Long Term Evolution (SRLTE) mode in which (a) the UE is served by the base station for data service even though the base station does not support CSFB (b) the UE registers to be served by the second RAN, and (c) the UE is set to engage in voice calls with the second RAN, wherein the registering occurs without the UE engaging in registration signaling with the second RAN over the interconnection between the first RAN and the second RAN, and wherein the second mode is a CSFB mode in which, in response to the base station not supporting CSFB, the UE declines to be served by the base station and the UE instead is served directly by the second RAN.

12. The UE of claim 11 , wherein the home service provider has a first PLMN ID having the predefined value and a second PLMN ID having a second, different predefined value, wherein determining whether the detected PLMN ID of the home service provider has the predefined value that is associated with operating in the first mode comprises determining whether the detected PLMN ID of the home service provider has the predefined value rather than the second predefined value.

13. The UE of claim 11 , wherein controlling, based on the determination of whether the detected PLMN ID of the home service provider has the predefined value associated with operating in the SRLTE mode, whether the UE operates in the SRLTE mode or rather operates in the CSFB mode comprises causing the UE to operate in the first mode only if the determination is that the detected PLMN ID of the home service provider has the predefined value associated with operating in the first mode.